Chang Hengtai, Chang Jun, Huang Qingjie, Wang Qiang, Tian Changbin, Wei Wei, Liu Yuanyuan
School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Jinan 250100, China.
Sensors (Basel). 2015 Apr 22;15(4):9582-91. doi: 10.3390/s150409582.
The division process used in a DFB diode laser-based optical gas sensor was studied to improve the immunity to laser power variation. Residual amplitude modulation (RAM) in wavelength modulation spectroscopy (WMS) detection was eliminated by intensity normalization using a division process. As a result the detected harmonic signals showed a significant improvement in line shape. For the first harmonic (1f) signal, Bias was improved from 38.7% to 1.2%; Baseline Difference was improved from 2.7% to 0.69% and Asymmetry was improved from 15.4% to 0.22%. For the second harmonic (2f) signal, the Asymmetry Coefficient was improved from 103% to 5.1%. Moreover the division process can further suppress the influence of unstable laser power. As a result, for the 1f signal, stable detection with a variation coefficient of 0.59% was obtained over a wide dynamic range (0.38-8.1 mW). For the 2f signal, stable detection with a variation coefficient of 0.53% was obtained from 0.64 mW to 8.27 mW. The test results showed a good agreement with the theoretical analysis and the proposed method has considerable potential application in gas sensing.
研究了基于分布反馈（DFB）二极管激光器的光学气体传感器中所采用的除法处理过程，以提高对激光功率变化的抗扰性。在波长调制光谱（WMS）检测中，通过使用除法处理进行强度归一化，消除了残余幅度调制（RAM）。结果，检测到的谐波信号在谱线形状上有显著改善。对于基波（1f）信号，偏差从38.7%提高到1.2%；基线差异从2.7%提高到0.69%，不对称性从15.4%提高到0.22%。对于二次谐波（2f）信号，不对称系数从103%提高到5.1%。此外，除法处理可以进一步抑制不稳定激光功率的影响。结果，对于1f信号，在宽动态范围（0.38 - 8.1 mW）内获得了变化系数为0.59%的稳定检测。对于2f信号，在0.64 mW至8.27 mW范围内获得了变化系数为0.53%的稳定检测。测试结果与理论分析吻合良好，所提出的方法在气体传感方面具有相当大的潜在应用价值。
